1. Field of Invention
This invention relates to artificial feet and is particularly directed to an artificial foot having quick release means for attaching said foot to a socket and having self-centering foot means for keeping said foot properly aligned with the leg portion thereof.
2. Prior Art
Artificial legs and other artificial devices of this category in the prior art have a fairly typical construction. Thus, a typical artificial leg comprises a socket which is fitted to the amputee's stump and a joint is provided at the knee which provides a hinge comparable to that of a natural knee. The hinge may be of a ball and socket type. Typically, there is an artificial foot at the end of the leg attached to it by a joint. This joint may also be a ball and socket joint. When fitted with such an artificial leg, the amputee is enabled to walk and perform various activities, but within quite stringent limitations. Obviously, the amputee does not have the control of the knee joint that he would have with a natural leg. Furthermore, the artificial foot must, of course, be aligned with the leg and, of course, there is no control for this comparable with that of a natural foot. This imposes very severe limitations when activities requiring any significant degree of freedom of motion are considered.
To overcome these limitations, it has been proposed to provide an artificial leg in the form of a stem or peg, having no knee joint, and having a generally semi-spherical member secured to the distal end of the stem in lieu of a foot. Such a device is covered by my prior patent, U.S. Pat. No. 3,707,731, issued Jan. 2, 1973. With this structure, the semi-spherical member is symmetrical about the stem or leg so that there is no problem of alignment and the stem is attached to the socket through a bearing which provides for 360.degree. of rotation. Hence, the position of the semi-spherical "foot" is always relatively the same. Moreover, the semi-spherical "foot" is constructed to provide a shock absorbing effect and to allow angular tilting of the "foot" relative to the stem or leg. It has been found that this structure provides vastly greater and more reliable support in playing golf or in similar athletic activities.
Although the device of my prior patent provides considerable functional improvement over conventional artificial legs. It has been found that it does not adjust to tilted surfaces as rapidly as might be desired and does not always return to its original position as rapidly as might be desired when it is lifted from the tilted surface. Furthermore, although the artificial leg of my prior patent has numerous functional advantages for the amputee, it is not as aesthetically attractive as a conventional artificial foot. Thus, for social purposes, the conventional artificial foot may be desirable. It would be highly desirable for the amputee to be able to rapidly switch, as desired, from the more functional "peg" of my prior patent to the more aesthetic conventional foot. Unfortunately, as noted above, artificial legs conventionally include a socket which is fitted to the amputee's stump. Thus, when not attached for use, an artificial leg is a bulky and cumbersome device and it would be quite burdensome and annoying to be required to carry one while wearing another.
A search in the United States Patent Office has revealed the following references:
______________________________________ U.S. PAT. NO. INVENTOR ISSUED ______________________________________ 3,706,465 E. J. Olowinski Dec. 19, 1972 3,906,552 A. L. Weber Sep. 23, 1975 4,007,496 R. Glabiszwski Feb. 15, 1977 4,564,365 R. A. Winer et al Jan. 14, 1986 ______________________________________
The patent to Winer et al teaches a quick change mechanism for permitting the rapid exchange of artificial legs. However, the Winer et al mechanism is complex and is not designed to provide strong omnidirectional support as is needed for athletic activities. Furthermore, substantial modification and precise refitting of an existing artificial leg would be required to enable its use with the quick change mechanism of Winer et al. Thus, none of the prior art artificial legs have been entirely satisfactory.